1. Field of Invention
This invention relates to a power assisted wrenching tool and, in particular, to a wrenching tool for attachment of fasteners in loose and interference fit applications.
2. Brief Statement of the Prior Art
Threaded fasteners are frequently used in loose fit applications in which it is difficult to work from both sides of the workpiece. This occurs quite frequently In the aerospace industry, and a particular fastening system has been developed in this industry. This system employs frangible fasteners comprising a bolt with a threaded nut member having a threaded collar and a distal wrenching ring separated by a notched section that provides a predetermined limiting torque which when exceeded, permits the wrenching ring to shear from the threaded collar, leaving the latter in place at a precise, predetermined tensile loading on the bolt member. Often, the threaded collar has an upset portion, usually a slightly elliptical shape, to provide a frictional spring lock to prevent the fastener from spinning off in the event that the residual tension on the fastener is lost. Typically, these fasteners are used both in loose and interference fit applications, and in the former applications it has been the practice to use a drive tool having a center key which is inserted into a broached keyway of the bolt to hold the bolt stationary while the threaded collar is applied.
Typically, the key is mounted in a keyway broached in the center core of a key holder member of the wrenching tool. The holder member is slideably received in a central through bore of the driven, socket member. The key is fixedly secured in the core of the holder member usually by a set screw. This attachment is cumbersome and causes delays and difficulties in changing the tool from the application of fasteners in interference fit and loose fit applications, since in only the latter is the key necessary. Also, the key often breaks during use and it is necessary to replace broken and worn keys, again a time consuming operation with the customary set screw lock. occasionally, the key becomes jammed in a bolt during the application of a threaded fastener and, when this occurs, the tool is immobilized and difficulties are experienced in removing the tool from the work.